Electric vehicle battery pack

Abstract: An electric vehicle battery pack including a plurality of batteries (6) connected together in an underlying tray (8). The tray (8) preferably has a plurality of pockets (20) therein, each one for receiving an individual battery (6). The batteries (6) are interlocked one to the next and held in place in the tray (8) by a housing (10) which bears down on the batteries (6) by means of a resilient spacer (36) positioned between the tops of the batteries (6) and the ceiling of the housing (10). The pack forms a structural part of the vehicle in which it is used.

Description: This invention relates to a battery pack for powering an electric vehicle as set forth in the preamble of claim 1. Electric vehicles with or without a supplemental internal combustion (IC) engine (ie, hybrid electric vehicle) require on-board batteries to power their electric drive systems. The performance requirements of electric vehicles dictate the need for connecting many batteries together into a variety of configurations depending on the design of the vehicle. Batteries so connected together are known as a battery pack. A battery pack comprises a plurality of individual batteries electrically connected one to the other, it is anchored to the vehicle and it will typically include a number of accessory electronic components for controlling the charge and discharge performance of the pack. The problems associated with packaging and positioning of a large mass within the vehicle becomes even more complicated when the vehicle design necessitates that the batteries be stacked in tiers on top of each other as is often required to maximise energy storage potential whilst minimising space utilisation within the vehicle. The battery pack can approach 50 percent of the weight of the vehicle especially when the batteries are of the lead-acid variety. In some cases so many batteries are required to satisfy the power demands of a vehicle that layers of batteries are stacked one on top of the other in a tier and these many batteries must be securely retained in both the horizontal and vertical directions for minimising dynamic effects on the vehicle. Due to the size and mass of the battery packs, the structural ramifications to the vehicle are considerable and the location of the battery pack and configuration has a direct and significant impact on the ride, handling, and performance of the vehicle. The manner in which the batteries are packaged and retained in the vehicle are so crucial to the function of the vehicle that often the battery pack forms a structural part of the vehicle. The hold-down devices for the batteries must be lightweight yet adequate to minimise any movement of the batteries in the pack. The stacking of batteries in tiers introduces several problems that must be considered in the battery pack hold-down system. The batteries must be firmly held vertically for elimination of bounce and associated noise while at the same time they also must be held horizontally to minimise dynamic affects on the handling of the vehicle. At the same time, it is necessary to minimise the weight of the hold-down system so that the performance and the range of the vehicle is not unnecessarily compromised. Finally due to the material used to form the battery cases (ie, typically injection-moulded polypropylene), batteries have tendencies to creep away from pressure points introduced with the hold-down fastening systems commonly seen today, eg, for SLI applications, resulting in a loosening of the batteries in the pack and consequent movement thereof in the vehicle. It is a principal object of the present invention to package an electric vehicle battery pack, stacked or unstacked, in such a way that the batteries remain tightly packed and environmentally sealed, the packaging contributes to the structural integrity of the vehicle, and the pack is not a detriment to the performance of the vehicle. It is a further object of the present invention to provide a packaging scheme with minimal fasteners and parts which allows considerable design flexibility for a variety of battery pack configurations. These and other objects and advantages of the present invention will become more readily apparent from the description thereof which follows. A battery pack for an electric vehicle according to the present invention is characterised by the features specified in the characterising portion of claim 1. The present invention broadly contemplates an electric vehicle battery pack comprising a plurality of batteries connected together and nesting in an underlying supporting tray. The ends of the batteries are securely joined together by an interlock device for further preventing any relative movement between adjacent batteries in the pack. The supporting tray comprises a plurality of intersecting, upstanding walls which stiffen the tray and define a plurality of pockets, each receiving one of the batteries. A peripheral flange extends outwards of the upstanding walls for further strengthening of the tray and for mounting of battery hold-downs. The battery hold-down comprises a housing enclosing the pack which housing comprises a ceiling wall, a plurality of side walls depending from the ceiling wall and a peripheral flange extending outwards from the edges of the side walls opposite the ceiling wall and overlying the peripheral flange on the supporting tray. A resilient spacer (eg, foraminous polymer, rubber, or spring-biased feet) is compressed between the ceiling wall and the tops of the batteries. Fasteners secure the peripheral flanges together so as to provide a rigid structure which provides structural strength to the vehicle whilst substantially immobilising the batteries therein against movement. The present invention further contemplates a battery pack of the type described above comprising at least two tiers of batteries wherein the lowest tier nests in the support tray and supports the upper tier, and an interlock means is provided intermediate the tiers. The interlock means has recesses therein adapted to receive and nest with the batteries in the upper and lower tiers so as to prevent relative movement between adjacent batteries. In one embodiment, the interlock means is itself a tray which nests with the batteries of an upper tier battery and the top of a lower tier and interlocks with a next adjacent intermediate tray in the pack. In another embodiment, the interlock means will include sockets on the ends of the battery container and a connecting plug comprising a rigid body portion having a plurality of tongues depending therefrom and engaging sockets on adjacent batteries. According to a preferred embodiment of the invention, there is provided a battery pack comprising a plurality of individual batteries connected together side-by-side and end-to-end in an underlying tray which supports the batteries. Most preferably, the pack will include at least two tiers of such batteries. The batteries each comprise a container for housing electrochemical components of the battery which, in turn, comprises a case and cover therefor. Means are provided on opposite ends of the container for interlocking each battery to the next adjacent battery in the pack. The interlocking means itself comprises at least one socket in the ends of each container, and an interlock plug overlying a set of sockets on adjacent batteries. The interlock plug comprises a rigid body which has a plurality of tongues depending from the body into the sockets of adjacent batteries and which holds the batteries together end-to-end, side-by-side, or both, depending on the configuration of the battery pack. The interlock plugs will include at least one passage therethrough, transversely of their length, for permitting such pack accessories as coolant tubes, interbattery connectors (eg, cables) and wiring systems for electronic controllers and/or monitors of the pack to pass therethrough to the end of the pack for connection to drive and/or control systems of the vehicle. When the pack contains two or more tiers the upper and lower batteries will nest in recesses formed in the interlock means. The underlying supporting tray comprises a plurality of intersecting upstanding walls which stiffen the tray and define a plurality of pockets, each one receiving one of the batteries. The floor of each pocket includes stiffening ribs which elevate the battery slightly above the floor of the pocket. The tray includes a peripheral flange extending outwards of the upstanding walls, and a housing encloses the pack and holds it securely in the tray. The housing includes a ceiling wall, a plurality of side walls depending from the ceiling wall and a peripheral flange extending outwardly from the edges of the side walls opposite the ceiling wall. The peripheral flange of the housing overlies the peripheral flange of the tray and is secured thereto by appropriate fastening means (eg, clips or bolts). The walls of the housing may include some openings therein for reducing its weight and allowing air circulation therethrough so long as the ability of the housing to stabilise the pack and add structural strength to the vehicle is not materially compromised. In order to achieve maximum rigidity with the minimum weight, the tray and housing will preferably comprise glass-fibre reinforced polypropylene wherein the tray will preferably include about 30 percent by volume glass and the housing about 10 percent by volume glass. Spring-like spacer means, preferably in the form of a sheet of resilient material (eg, rubber or foamed polymers), is provided between the ceiling wall of the housing and the tops of the batteries, which material is compressed when the housing is secured to the tray and acts like a spring to provide a downward force on the batteries. The spacer will most preferably comprise beaded, closed-cell polypropylene foam having a plurality of protuberances thereon engaging the tops of the batteries. The body of the interlock plug will preferably include upstanding walls which define a recess/nest for receiving and retaining the bottom of a battery in a superimposed tier of batteries. That is to say, when the battery pack includes more than one tier of batteries, the interlock means holding the tops of the batteries in the lower tier together serve to support the batteries in the upper tier and prevent the upper tier batteries from shifting laterally once they are each positioned in the respective recess/nest. The interlock plugs may be used with a single row of batteries aligned end-to-end or with two or more rows of side-by-side batteries in which latter case the interlock not only connects the batteries end-to-end but side-by-side as well. The interlock plug will preferably also include a snap-lock retainer tab which engages a projection on the battery container for securely holding the interlock plug in place on top of the batteries. The invention will better be understood when considered in the light of the following description of a specific, preferred embodiment thereof which is given hereafter in conjunction with the accompanying drawings, in which: Figure 1 is an isometric view of a battery pack in accordance with the present invention; Figure 2 is an exploded, isometric view of the battery pack in accordance with the present invention; Figure 3 is a side elevational view of one end of a battery forming part of the battery pack of the present invention; Figure 4 is a view taken in the direction 4-4 of Figure 3; Figure 5 is a view taken in the direction 5-5 of Figure 4; Figure 6 is an end view of a pair of batteries held together by an interlock means (shown in phantom) in accordance with the present invention; Figure 7 is an isometric view of an interlock means in accordance with the present invention; Figure 8 is a partial plan view of a set of four batteries held end-to-end and side-by-side in accordance with the present invention; Figure 9 is a view taken in the direction 9-9 of Figure 8; Figure 10 is a view taken in the direction 10-10 of Figure 8; Figure 11 is a bottom view taken in the direction 11-11 of Figure 2 showing the inside of a housing of the battery pack; and Figure 12 is an alternative embodiment of an interlock means between upper and lower battery tiers. Figure 1 depicts a battery pack for an electric vehicle including an upper tier 2 and a lower tier 4 of individual batteries 6 all nested in a supporting tray 8 and securely held in place thereon by a housing 10 (shown in phantom). An accessory tray 12 is provided inside the housing 8 for mounting any of a variety of electronic devices for controlling and/or monitoring the charge, discharge, charge balance and performance of the pack. Alternatively, another row of batteries 6 may replace the tray 12. A console 14 is provided at the end of the pack for mounting additional control/monitoring devices and receiving wiring from within the pack. Figure 2 is an exploded view of the pack shown in Figure 1. The underlying supporting tray 8 includes a plurality of upstanding walls 16 and partitions 18 which together define a plurality of pockets 20, each receiving one of the batteries 6 in the lower tier 4. The pockets 20 have a floor 22 therein which in turn has ribs 24 extending upwardly therefrom for stiffening the tray 8. These reinforcing ribs 24 extend diagonally across said floor (22) and intersect in the middle thereof. A peripheral flange 26 extends about the perimeter of the support tray 8 and provides a means for attaching the housing 10 to the tray 8 whilst at the same time providing additional strength/stiffness to the tray 8. In addition to being nested within the pockets 20 of the tray 8, the batteries 6 are also interlocked one to the other at the top edges thereof by means of interlocking plugs 28 which are inserted into sockets 30 in the ends of the battery containers as will be discussed in more detail hereinafter. An accessory tray 12 in the upper tier of batteries replaces one of the rows of batteries 6 and will include sockets 32 and tongues 34 comparable to those found in the containers 30 and plugs 28 so that the accessory tray 12 will interlock with the adjacent batteries 6 in the pack in much the same manner as though it were a row of batteries 6. A layer of resilient material 36 is positioned in the housing 10 so as to press on the tops of the upper tier batteries. The resilient material will preferably comprise closed-cell, beaded polypropylene foam having a density of about 68.88 kg/m 3 (4.3 lbs/cubic foot) and is supplied by the Kaneka Texas Corporation, USA under the trade name of Eperan-pp. The polypropylene foam 36 will preferably include a plurality of oval protuberances 38 which contact the tops of the batteries 6 in the upper tier 2 and upon compression act like a spring pressing the battery pack firmly into the tray 8 when the housing 10 is secured to the tray 8. The housing 10 comprises an uppermost ceiling wall 40, depending side walls 42 and peripheral flange 44 extending outboard the side walls 42 for engaging the peripheral flange 26 of the support tray 8 and further stiffening the structure. Fastener means (not shown) join the flanges 26,44 securely together so as to provide a rigid structure which provides structural strength to the vehicle in which the battery pack is installed whilst substantially immobilising the batteries 6 against movement relative to one another. A gasket (not shown) is provided between the flanges 26,44 for environmentally sealing the housing 10 to the tray 8. An opening 46 is provided in the end of the housing 10 to accommodate wires and cables 48 leaving the pack via the console 14. Vertical ribs 50 are provided on the inner surfaces of the side walls 42 for engaging recesses 52 in the ends of the plugs 28, and serve not only to guide the housing 10 into place when it is positioned over the batteries but also to further lock the plugs 28 in place and prevent shifting of the batteries within the housing 10. As best shown in Figure 7, the interlock plug 28 includes a plurality of depending tongues 54. The tongues 54 mate with the sockets 30 in the ends of the batteries 6 shown in Figure 2. In the particular embodiment shown, the plug 28 serves not only to join the batteries 6 end-to-end, but is also long enough to join batteries side-by-side in the battery pack as illustrated in Figures 6 and 8. However, in a situation where only one row of batteries 6 is needed the length of the plug 28 would be shorter and would only interlock the batteries end-to-end. Recesses 52 in the ends of the plug 28 are adapted to receive the ribs 50 on the inside surfaces of the housing 10 to both guide the housing 10 into position during placement of the housing 10 over the batteries 6 and to prevent any shifting of the batteries in the direction of the long axis of the pack. Upstanding walls 56 define recesses 58 forming nests for receiving and holding the bottoms of batteries in the next superimposed tier 2 of batteries 6. Channels 60 extend transversely of the plug 28 for passage of battery cables 62 therethrough for electrically interconnecting adjacent batteries together in the pack (see Figure 8). The channels 60, or alternatively one or more other channels 64, may also be used to route other wires or wire bundles (eg, from electronic controllers/monitors of the pack) throughout the pack. A plurality of gussets 66 support floors 68 of the recesses 58. Snap-lock tabs 70 are provided at the ends of the plugs 28 and each includes a camming surface 72 and shoulder 74. When the plug 28 is positioned over a set of sockets to be interlocked together, each camming surface 72 engages a projection 76 (eg, an elongated rail) formed on a respective side of a battery container 80 of a respective battery 6 and causes the respective snap-lock tab 70 to flex outwardly and then snap back to engage the shoulder 74 under the locking projection 76 and thereby permanently retain the plug 28 in position until such time as all the snap-lock tabs 70 are positively disengaged from the projections 76 on the battery containers 80. Figures 3-5 show a preferred embodiment of the battery container 80 comprising a case 82 having an outer wall 84 and a cover 86. A shelf 88 extends outwards of the wall 84 and has the socket 30 of the interlocking means formed therein. Exterior ribbing 90 depends from the shelf 88 and projects outwardly from the wall 84 to reinforce the wall 84 and prevent bulging of the case 82 incident to the internal pressures that can build up therein in many battery systems, eg, valve-regulated, gas recombinant-type lead-acid batteries. A secondary cover 92 is provided and interacts with the primary cover 86 to define a venting manifold for receiving and venting any gases that might otherwise escape from the battery as is common with any modern battery designs. A terminal 94 is provided at each end of the battery 6 for electrically coupling to similar terminals on adjacent batteries via interbattery connector cables 62 (see Figure 10). Figures 6-10 show various views of the batteries 6 connected side-by-side (ie, Figure 6) and end-to-end (ie, Figure 8). More specifically, Figure 6 shows in phantom the interlock plug 28 locked in position between adjacent side-by-side batteries 6 and with the snap-lock tabs 70 engaging projections 76 that extend the length of the battery on both sides thereof. Figure 8 is a plan view of four batteries 6 coupled together end-to-end (ie, 6(A)-6(B) and 6(C)-6(D) respectively) and side-by-side (ie, 6(A)-6(C) and 6(B)-6(D)) by means of the plug 28 inserted into the respective sockets 30. A cable 62 having appropriate terminal connectors 96 thereon engages the terminals 94 of the end-to-end batteries 6 and passes through the channel 60 in the plug 28. Figure 9 depicts the plug 28 with its tongues 54 inserted into the sockets 30 with a bottom wall 98 of the plug 28 resting squarely on top of the upper surface of the shelf 88 which provides an excellent bearing surface over which to distribute the weight of any overhead batteries 6 (shown in phantom nesting in the recesses 58). Figure 10 is a view similar to Figure 9 but taken through the length of the channel 60 showing the inter-battery connecting cable 62. Figure 11 is a view taken in the direction 11-11 of Figure 2 showing the inside of the housing 10. The view shows the underside of the peripheral flange 44, the resilient material 36, protuberances 38 on the material 36, and vertical ribs 50 on the walls 42. Also shown in phantom are plugs 28 with their end recesses 52 engaging the vertical ribs 50 on the inside of the housing 10 as described above. Figure 12 depicts another embodiment of a means for interlocking the batteries one to the other end-to-end and top-to-bottom. More specifically Figure 12 shows a tray 99 which is adapted to fit between tiers of a multi-tiered pack. The tray 99 has recesses 100 formed in the upper face thereof, each for receiving the bottom of a respective battery in an upper tier, and second recesses 102 formed in the lower face thereof, each for receiving the top of a respective battery in a lower tier. Recesses 100, 102 are circumscribed by a frame 104, the ends of which have a series of dovetail mortises 106 and tenons 108 thereon adapted to mate with ends of similar trays positioned between upper and lower batteries 6 in the next adjacent set of batteries. Whilst the invention has been described primarily in terms of specific embodiments thereof, the scope of the invention is not intended to be limited thereto but rather only to the extent set forth hereafter in the claims which follow.

Claims: A battery pack for an electric vehicle comprising a plurality of individual batteries (6) connected together and nesting in an underlying supporting tray (8), and interlock means (28,30) engaging the ends of said batteries (6) for preventing relative movement between adjacent batteries (6) in the pack, characterised in that said supporting tray (8) comprises a plurality of intersecting, upstanding walls (16) stiffening said tray (8) and defining a plurality of pockets (20) each receiving a respective one of said batteries (6) and a peripheral flange (26) extending outwards of said upstanding walls (16); there is a housing (10) enclosing said pack, said housing (10) comprising a ceiling wall (40), a plurality of side walls (42) depending from said ceiling wall (40), and a peripheral flange (44) extending outwardly from the edges of said side walls (42) opposite said ceiling wall (40) and overlying said peripheral flange (26); there is a resilient spacer (36) compressed between said ceiling wall (40) and the tops of the batteries (16), and there are fastener means joining said peripheral flanges (26,44) securely together so as to provide a rigid structure which provides structural strength to said vehicle whilst substantially immobilising the batteries (6) against movement relative to one another. A battery pack for an electric vehicle according to claim 1, in which the pack comprises a lower tier of said batteries (6) nesting in said supporting tray (8), an upper tier of said batteries (6) overlying and supported by said lower tier, and interlock means (28,30) intermediate said tiers, said interlock means (28,30) having recesses (58) therein which nest over said batteries (6) in said upper and lower tiers, and said interlock means (28,30) preventing relative movement between adjacent batteries (6) in the pack. A battery pack according to claim 2, in which said interlock means comprises an interlock tray (99) having a first recess (100) in an upper face for receiving the underside of a battery (6) in said upper tier, a second recess (102) in a lower face for receiving the topside of a battery in said lower tier and coupling means (106,108) on a perimeter frame (104) of said interlock tray (99) for coupling said tray (99) to a next adjacent interlock tray (99) in said pack. A battery pack according to claim 3, in which said coupling means comprises mortise and tenon means (106,108) mating with complementary mortise and tenon means (106,108) on the next adjacent interlock tray (99). A battery pack according to claim 4, in which the mating mortise and tenon means (106,108) form a dovetail joint. A battery pack according to claim 2, in which said interlock means comprises at least one socket (30) formed in the ends of each battery (6) and a plug (28) overlying a set of sockets (30) on adjacent batteries (6) said plug (28) comprising a rigid body and a plurality of tongues (54) depending from said body into the sockets (30) of said set. A battery pack comprising a plurality of individual batteries (6) connected together side-by-side and end-to-end in an underlying tray (8) supporting said batteries (16), said batteries each comprising a container (80), characterised in that there are locking means on opposite ends of said container (80) for locking each container (80) to the next adjacent battery (6) in the pack, said locking means comprising a socket (30) in each of said containers (80) and an interlock member (28) overlying a set of sockets (30) on adjacent batteries, said interlock member (28) comprising a rigid body and a plurality of tongues (54) depending from said body into the sockets (30) of said set to hold said adjacent batteries (6) together; and there are anchoring means (10,18,20) for holding said batteries (6) securely in said tray (8). A battery pack according to claim 7, in which said anchoring means (10) engages said interlock members (28). A battery pack according to claim 8, in which said anchoring means (10) engages said tray (8). A battery pack according to claim 7, in which said tray (8) comprises a plurality of intersecting, upstanding walls (16) stiffening said tray and defining a plurality of pockets (20) each receiving a one of said batteries (6). A battery pack according to claim 10, in which each of said pockets is defined by a floor (22) having reinforcing ribs (24) upstanding therefrom and supporting the respective battery (6) thereon. A battery pack according to claim 11, in which said reinforcing ribs (24) extend diagonally across said floor (22) and intersect in the middle thereof. A battery pack according to claim 10, in which said tray (8) includes a peripheral flange (26) extending outwards from said upstanding walls (16) and said anchoring means comprises a housing (10) enclosing said pack, said housing (10) comprising a ceiling wall (40), a plurality of side walls (42) depending from said ceiling wall (40), and a peripheral flange (44) extending outwardly from the edges of said side walls (42) opposite said ceiling wall (40) and overlying said peripheral flange (26), and fastener means joining said peripheral flanges (26,44) securely together. A battery pack according to claim 7, in which said anchoring means comprises a housing (10) enclosing said pack and secured to said tray (8), said housing (10) comprising a ceiling wall (40) overlying said pack and a plurality of side walls (42) depending from said ceiling wall (40) circumscribing said pack. A battery pack according to claim 14, in which said anchoring means includes a resilient spacer (36) compressed between said ceiling wall (40) and the tops of said batteries (6). A battery pack according to claim 15, in which said spacer (36) comprises a foamed polymer. A battery pack according to claim 7, in which said body of the interlock member (28) includes at least one passage (60,64) therethrough transversely of its length for receiving interbattery electrical connectors, pack control wiring and pack coolant conduits. A battery pack according to claim 7, in which said pack includes a plurality of tiers of batteries (6) connected together and said body of the interlock member (28) includes upstanding walls (56) defining nests receiving respective batteries (6) in a superimposed tier. A battery pack according to claim 7, in which a single said interlock member (28) engages adjacent batteries (6) which are positioned end-to-end and side-by-side in the pack. A battery pack according to claim 7, in which each of said containers (80) includes a lateral projection (76) extending outwardly from an external wall (84) thereof and said interlock member (28) includes a retainer (70) having a shoulder (74) thereon for engaging said projection (76) and securely fastening said member (28) to said batteries (6). A battery pack according to claim 7, in which the underside (98) of said body (28) engages said container (80) on top of said sockets (30). A battery pack according to claim 20, in which said projection comprises a rib (26) extending the length of said container (80). A battery pack according to claim 14, in which said tray (8) and said housing (10) are formed from a glass-reinforced polymer. A battery pack according to claim 23, in which said polymer comprises polypropylene. A battery pack comprising a plurality of individual batteries (6) connected together side-by-side and end-to-end in an underlying tray (8) supporting said batteries (6), said batteries (6) each comprising a container (80) having a case (82) and cover (86), a shelf (88) on said case (82) overhanging each end of said battery (6) and confronting a shelf (88) on a next adjacent battery (6) in the pack, a socket (30) in each of said shelves (88), an interlock member (28) comprising a rigid body overlying a set of adjacent shelves (88) and a plurality of tongues (54) depending from said body into said sockets (30) for holding said adjacent batteries (6) together, and anchoring means (10) engaging said tray (8) and holding said batteries (6) securely in said tray (8). A battery pack according to claim 16, in which said foamed polymer comprises beaded polypropylene.

Inventors: BOYS WILLIAM EDWARD, BROUNS DANIEL ROBERT, GRESLEY ROSS ALAN, HARRIS BRENT ALAN, WATERS JOHN EUGENE, BOYS, WILLIAM EDWARD, BROUNS, DANIEL ROBERT, GRESLEY, ROSS ALAN, HARRIS, BRENT ALAN, WATERS, JOHN EUGENE
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1994
Main classification: H01M2
IPC codes: H01M2